* {
    margin: 0;
    padding: 0;
}

#app {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    height: 100vh;
}

.steps {
    display: flex;
}

.steps .steps_item {
    position: relative;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    border: 3px solid #E0E0E0;
    line-height: 30px;
    text-align: center;
    color: #666;
    margin-right: 50px;
    transition: border .5s ease-out;
}

.steps .steps_item.active {
    border-color: #3498DB;
}

.steps .steps_item .line {
    position: absolute;
    right: -53px;
    top: 50%;
    transform: translateY(-50%);
    width: 50px;
    height: 5px;
    background-color: #E0E0E0;
    transition: background .5s ease-out;
}

.steps .steps_item .line.active {
    background-color: #3498DB;
}

.steps .steps_item:last-child .line {
    display: none;
}

.btns {
    display: flex;
    margin-top: 50px;
}

.btn {
    width: 100px;
    height: 36px;
    line-height: 36px;
    text-align: center;
    color: #fff;
    background-color: #3498DB;
    margin-right: 20px;
    border-radius: 5px;
    cursor: pointer;
}

.btn_click {
    animation: shake 1.3s ease-in-out;
}

@keyframes shake {
    0% {
        -webkit-transform: scale(1);
        transform: scale(1)
    }
    14% {
        -webkit-transform: scale(1.1);
        transform: scale(1.1)
    }
    28% {
        -webkit-transform: scale(1);
        transform: scale(1)
    }
    42% {
        -webkit-transform: scale(1.1);
        transform: scale(1.1)
    }
    70% {
        -webkit-transform: scale(1);
        transform: scale(1)
    }
}

.btn.disable {
    background-color: #E0E0E0;
    cursor: not-allowed;
}